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  <h1>Keys</h1>
  <p>The function of the keyboard can be extensively customized in Eclipse using the <a class="command-link" href=
  'javascript:executeCommand("org.eclipse.ui.window.preferences(preferencePageId=org.eclipse.ui.preferencePages.Keys)")'>
  <img src="PLUGINS_ROOT/org.eclipse.help/command_link.svg" alt="command link"> <strong>General &gt; Keys</strong></a>
  preference page. Within Eclipse, key strokes and key sequences are assigned to invoke particular commands.</p>
  <h2>Key Strokes, Key Sequences, and Key Bindings</h2>
  <p>A 'key stroke' is the pressing of a key on the keyboard, while optionally holding down one or more of these
  modifier keys: <code>Ctrl</code>, <code>Alt</code> (<code>⌥</code> on macOS), <code>Shift</code>, or <code>⌘</code>
  (only on macOS.) For example, holding down <code>Ctrl</code> then pressing <code>A</code> produces the key stroke
  <code>Ctrl+A</code>. The pressing of the modifier keys themselves do not constitute key strokes.</p>
  <p>A 'key sequence' is one or more key strokes. Traditionally, Emacs assigned two or three key stroke key sequences
  to particular commands. For example, the normal key sequence assigned to <code>Close All</code> in emacs is
  <code>Ctrl+X Ctrl+C</code>. To enter this key sequence, one presses the key stroke <code>Ctrl+X</code> followed by
  the key stroke <code>Ctrl+C</code>. While Eclipse supports key sequences of arbitrary lengths, it is recommended that
  keyboard shortcuts be four key strokes in length (or less).</p>
  <p>A 'key binding' is the assignment of a key sequence to a command.</p>
  <h2>Schemes</h2>
  <p>A 'scheme' is a set of bindings. Eclipse includes two schemes:</p>
  <ul>
    <li>Default</li>
    <li>Emacs (extends Default)</li>
  </ul>
  <p>The <em>Default</em> scheme contains a general set of bindings, in many cases recognizable as traditional key
  sequences for well known commands. For instance, <code>Ctrl+A</code> is assigned to <code>Select All</code>, and
  <code>Ctrl+S</code> is assigned to <code>Save</code>.</p>
  <p>The <em>Emacs</em> scheme contains a set of key bindings familiar to users of Emacs. For instance, <code>Ctrl+X
  H</code> is assigned to <code>Select All</code>, and <code>Ctrl+X S</code> is assigned to <code>Save</code>.</p>
  <p>It is important to understand why the <em>Emacs</em> scheme says that it 'extends Default'. The <em>Emacs</em>
  scheme is not a complete set of bindings like the <em>Default</em> scheme. Rather, it borrows from the
  <em>Default</em> scheme where possible, only defining explicit Emacs-style bindings where they vary from the
  <em>Default</em> scheme. Generally, only well known commands like <code>Select All</code>, <code>Save</code>, etc.
  have specific Emacs key sequences associated with them.</p>
  <p>Choose the scheme you are most comfortable with by changing the 'Scheme' setting on the keys preference page. If
  you choose the <em>Default</em> scheme, all <em>Emacs</em> bindings are ignored. If you choose the <em>Emacs</em>
  scheme, explicit Emacs-style key sequence assignments take precedence over any conflicting assignments in the
  <em>Default</em> scheme.</p>
  <h2>Contexts</h2>
  <p>Key bindings can vary based on the current context of Eclipse.</p>
  <p>Sometimes the active part might be a Java file editor, for instance, where a different set of key sequence
  assignments may be more appropriate than if the active part was an html file editor. As a specific example, typically
  <code>Ctrl+B</code> is assigned to <code>Build</code> in a context such as Java file editing, while
  <code>Ctrl+B</code> is assigned to <code>Make Text Bold</code> in a context such as HTML file editing. This context
  is usually determined by the active part, but it can be influenced by the active window or dialog as well. If the
  active part does not choose a particular context, the workbench will set the active context to <em>In
  Windows</em>.</p>
  <p>Eclipse includes a number of different contexts. Some examples are:</p>
  <ul>
    <li>In Dialogs and Windows</li>
    <li>In Windows (extends In Dialogs and Windows)</li>
    <li>In Dialogs (extends In Dialogs and Windows)</li>
    <li>Editing Text (extends In Windows)</li>
    <li>Editing Java Source (extends Editing Text)</li>
    <li>Debugging (extends In Windows)</li>
    <li>Debugging Java (extends Debugging)</li>
    <li>In Console</li>
    <li>Editing Ant buildfiles<br>
    <br></li>
  </ul>
  <p>Much like configurations, contexts can extend other contexts. For example, the <em>Editing Java Source</em>
  context borrows key bindings from the <em>Editing Text</em> context, which in turn borrows key bindings from the
  <em>In Windows</em> context.</p>
  <p>Note: It is not recommended to promote a key binding to a context which it extends. For example, it is not
  recommended to move an <em>Editing Text</em> key binding to the <em>In Dialogs and Windows</em> context. This may
  have unexpected results.</p>
  <p>It is possible for some key bindings to work in dialogs. Those key bindings are assigned to the <em>In Dialogs and
  Windows</em> context. One example of such a key binding is the key binding for "cut". It is possible to change these
  key bindings. For example, it is possible to have Ctrl+X as cut in dialogs, but Ctrl+W as cut in windows.</p>
  <h2>Platform and Locale</h2>
  <p>Key bindings also vary by platform and locale. On the macOS platform, <code>⌘+S</code> is assigned to
  <code>Save</code>, instead of the usual <code>Ctrl+S</code>. On Chinese locales (zh), <code>Alt+/</code> is assigned
  to <code>Content Assist</code>, instead of the usual <code>Ctrl+Space</code>.</p>
  <p>The current platform and locale is determined when Eclipse starts, and does not vary over the course of an Eclipse
  instance.</p>
  <h2>Customizing Key Bindings</h2>
  <p>With multi-stroke key sequences, schemes, and contexts, there are a lot of things to keep in mind when customizing
  key bindings. To make things easier, all key customization is done on the <a class="command-link" href=
  'javascript:executeCommand("org.eclipse.ui.window.preferences(preferencePageId=org.eclipse.ui.preferencePages.Keys)")'>
  <img src="PLUGINS_ROOT/org.eclipse.help/command_link.svg" alt="command link"> <b>General &gt; Keys</b></a> preference
  page.</p>
  <p><img src="../../images/keys1.png" alt="Keys preference page the About command with no binding"></p>
  <p>In this example we want to bind <b>CTRL+5</b> to the About command. By default the keys preference page will show
  you all possible keybindings. You can see the About command listed in the Help category. You can bind the command by
  putting focus in the Binding text box and pressing CTRL and 5 like you would if you were executing the command.</p>
  <p><img src="../../images/keys2.png" alt="Keys preference page the About command bound to CTRL+5"></p>
  <p>When you type CTRL+5 you have created a binding for About. The right-most column will indicate that this is a user
  binding by displaying a <b>U</b>. If there was a conflict with another key, this column would also display a
  <b>C</b>. The binding will be in the default context, "In Windows". You can now use the When combo box to change the
  key binding context (for example, to move this binding to "Editing Text").</p>
  <p>If you wanted to add a second key binding to About, you can use the <b>Copy Command</b> button to create a second
  command entry for you to bind another key to. If you want to delete a binding, you can either use the <b>Remove
  Binding</b> button or simply give focus to the Binding text box and hit <b>Backspace</b>.</p>
  <h2>The Dynamic Nature of Key Bindings</h2>
  <p>Key bindings are provided by plug-ins, and in Eclipse, plug-ins can be added or removed. This can cause key
  bindings declared by these plug-ins to be added or removed. Eclipse stores custom key bindings in a way to compensate
  for this. Consider the example above where <code>CTRL+6</code> was assigned to <code>About</code> in the
  <em>Default</em> scheme. Say you install a new plug-in that assigns <code>CTRL+6</code> to a particular command.
  Eclipse will preserve your assignment to <code>About</code>.</p>
  <h2>Conflict Resolution</h2>
  <p>There are only a finite number of simple, common key strokes available to assign to a multitude of commands. We
  have seen that scheme, context, platform, and locale all partition key sequence assignments into domains where they
  don't conflict with one another. Consider the case for <code>Ctrl+B</code> above if contexts did not exist. One
  plug-in would assign <code>Ctrl+B</code> to <code>Build</code>, the other plug-in would assign <code>Ctrl+B</code> to
  <code>Make Bold Text</code>. How would Eclipse properly resolve this conflict?</p>
  <p>Though conflicts are drastically reduced by employing the above mechanisms, they can still occur. Two plug-ins,
  independent of one another, could assign the same key sequence to different commands with the same context, scheme,
  platform, and locale. Consider if a plug-in assigned <code>Ctrl+F4</code> in the <em>In Windows</em> context and
  <em>Default</em> scheme to one of its commands. This directly conflicts with Eclipse assigning <code>Ctrl+F4</code>
  to the close command in the same context and scheme.</p>
  <p>This is a conflict. It wouldn't be proper to invoke both commands, nor would it be proper to simply choose one of
  the two commands to receive the key stroke. We pop up the Key Assist Dialog with the conflicting commands and allow
  the user to select one. The Key Assist Dialog is the same dialog that displays command choices for multiple key
  stroke key bindings. For example, if 2 commands were bound to <b>F12</b> you might see:</p>
  <p><img src="../../images/keys3.png" alt="Keys Assist dialog"></p>
  <p>If the user sets a keybinding and creates a conflict, the conflicting bindings will be displayed in the conflicts
  list. This can be used to navigate between conflicting keybindings so that they can be changed.</p>
  <p><img src="../../images/keys4.png" alt="Keys preference page conflict list"></p>
  <p>These types of conflicts can be resolved by explicitly assigning the key sequence to one of the commands, or
  remove it from the other.</p>
  <p>Another type of conflict can be caused by multiple-key stroke key sequences. For example, in the <em>Emacs</em>
  scheme, there are many multiple-key stroke key sequences beginning with the key stroke <code>Ctrl+X</code>.
  <code>Ctrl+X K</code> is assigned to <code>Close</code>. <code>Ctrl+X H</code> is assigned to <code>Select
  All</code>.</p>
  <p>As previously mentioned, the <em>Emacs</em> scheme borrows key bindings from the <em>Default</em> scheme. In the
  default scheme, <code>Ctrl+X</code> is assigned to <code>Cut</code>. Though the <em>Emacs</em> scheme doesn't
  explicitly redefine <code>Ctrl+X</code>, pressing <code>Ctrl+X</code> is required as part of many of its key
  bindings. In the <em>Emacs</em> scheme, when one presses <code>Ctrl+X</code>, one is half way to entering one of many
  possible assigned key sequences. One would not expect the <code>Cut</code> action to be invoked at this time.</p>
  <p>For this type of conflict, the rule is that the <code>Ctrl+X</code> key sequence assigned to <code>Cut</code>
  would be ignored. Otherwise, it would not be possible to complete many of the key bindings in the <em>Emacs</em>
  configuration.</p>
  <h2>Export Key Bindings</h2>
  <p>The bindings can be exported to a CSV file. For this purpose, press the button <strong>Export CSV ...</strong>.
  This will launch a file dialog, where you can specify the location of the export file. Note: The export file is for
  reporting purposes only and <strong>can not be used to import</strong> the binding files into Eclipse.</p>
  <h2>Show Key Bindings When Command Is Invoked</h2>
  <p>For learning purposes, presentations or screen casts it is very helpful to show the corresponding key binding when
  a command is invoked. Whenever the command is invoked (via the keyboard or via menu clicks), the key binding, the
  command's name and description are shown on the screen.</p>
  <p><img src="../../images/show_key_bindings.png" alt="Key binding of triggered command shown on screen" style=
  "width: 40%"></p>
  <p>This can be activated via the check boxes in the <em>Show key binding when command is invoked</em> group on the
  <a class="command-link" href=
  'javascript:executeCommand("org.eclipse.ui.window.preferences(preferencePageId=org.eclipse.ui.preferencePages.Keys)")'>
  <img src="PLUGINS_ROOT/org.eclipse.help/command_link.svg" alt="command link"> <strong>General &gt; Keys</strong></a>
  preference page. To toggle this setting quickly, the command 'Toggle Show Key Bindings' can be used (e.g. via the
  Find Actions dialog).</p>
  <h3 class="related">Related Concepts</h3><a href="accessmain.htm">Accessibility features in Eclipse</a><br>
  <a href="../../tasks/tkeybindings.htm">Changing the key bindings</a><br>
  <a href="../help.htm">Help</a>
  <h3 class="related">Related Reference</h3><a href="fontsandcolors.htm">Font and color settings in Eclipse</a>
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